 /*******************************************************************************
  * Copyright (c) 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  ******************************************************************************/

 package org.eclipse.ui.internal.navigator;

 import java.util.HashSet ;
 import java.util.Set ;

 import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.ListenerList;
 import org.eclipse.ui.navigator.IExtensionActivationListener;
 import org.eclipse.ui.navigator.INavigatorActivationService;
 import org.eclipse.ui.navigator.INavigatorContentDescriptor;
 import org.eclipse.ui.navigator.INavigatorContentService;
 import org.eclipse.ui.navigator.INavigatorViewerDescriptor;

 /**
  * Stores information about programmatic bindings and activation settings.
  *
  */
 public class VisibilityAssistant implements IExtensionActivationListener {

     private final INavigatorViewerDescriptor viewerDescriptor;

     private final Set programmaticVisibilityBindings = new HashSet ();

     private final Set programmaticRootBindings = new HashSet ();

     private final ListenerList listeners = new ListenerList();

     private final INavigatorActivationService activationService;

     /**
      * Notifies clients of changes in extension visibility or activation.
      *
      */
     public interface VisibilityListener {

         /**
          * Respond to the change in visibility or activation.
          *
          */
         void onVisibilityOrActivationChange();
     }

     /**
      * Create a visibility assistant for the given viewer descriptor.
      *
      * @param aViewerDescriptor
      * A non-nullviewer descriptor.
      * @param anActivationService
      * The activation service associated with the content service.
      */
     public VisibilityAssistant(INavigatorViewerDescriptor aViewerDescriptor,
             INavigatorActivationService anActivationService) {
         Assert.isNotNull(aViewerDescriptor);
         viewerDescriptor = aViewerDescriptor;

         activationService = anActivationService;
         activationService.addExtensionActivationListener(this);
     }

     /**
      * Dispose of any resources held onto by this assistant.
      *
      */
     public void dispose() {
         activationService.removeExtensionActivationListener(this);
     }

     /**
      *
      * @param theExtensions
      * The extensions that should be made visible to the viewer.
      * @param isRoot
      */
     public void bindExtensions(String [] theExtensions, boolean isRoot) {
         if (theExtensions == null) {
             return;
         }
         for (int i = 0; i < theExtensions.length; i++) {
             programmaticVisibilityBindings.add(theExtensions[i]);
             if (isRoot) {
                 programmaticRootBindings.add(theExtensions[i]);
             }
         }
         notifyClients();
     }

     /**
      * Add a listener to be notified when the visibility or activation state
      * associated with this assistant changes.
      *
      * @param aListener
      * a listener to be notified when the visibility or activation
      * state associated with this assistant changes.
      */
     public void addListener(VisibilityListener aListener) {
         listeners.add(aListener);
     }

     /**
      * Remove a listener to be notified when the visibility or activation state
      * associated with this assistant changes.
      *
      * @param aListener
      * a listener to be notified when the visibility or activation
      * state associated with this assistant changes.
      */
     public void removeListener(VisibilityListener aListener) {
         listeners.remove(aListener);
     }

     private void notifyClients() {
         Object [] clients = listeners.getListeners();
         for (int i = 0; i < clients.length; i++) {
             ((VisibilityListener) clients[i]).onVisibilityOrActivationChange();
         }
     }

     /**
      *
      * @param aContentDescriptor
      * The content descriptor of inquiry
      * @return True if and only if the content descriptor is <i>active</i> and
      * <i>visible</i> for the viewer descriptor and enabled for the
      * given element.
      */
     public boolean isVisibleAndActive(
             INavigatorContentDescriptor aContentDescriptor) {
         return isActive(aContentDescriptor) && isVisible(aContentDescriptor);
     }

     /**
      *
      * @param aContentDescriptor
      * The content descriptor of inquiry
      * @return True if and only if the given extension is <i>active</i>
      *
      * @see INavigatorContentService For more information on what <i>active</i>
      * means.
      * @see INavigatorActivationService#activateExtensions(String[], boolean)
      * @see INavigatorActivationService#deactivateExtensions(String[], boolean)
      */
     public boolean isActive(INavigatorContentDescriptor aContentDescriptor) {
         return activationService.isNavigatorExtensionActive(aContentDescriptor
                 .getId());
     }

     /**
      *
      * @param aContentExtensionId
      * The unique id of the content extension
      * @return True if and only if the given extension is <i>active</i>
      * @see INavigatorContentService For more information on what <i>active</i>
      * means.
      * @see INavigatorActivationService#activateExtensions(String[], boolean)
      * @see INavigatorActivationService#deactivateExtensions(String[], boolean)
      */
     public boolean isActive(String aContentExtensionId) {
         return activationService
                 .isNavigatorExtensionActive(aContentExtensionId);
     }

     /**
      *
      * @param aContentDescriptor
      * The content descriptor of inquiry
      * @return True if and only if the given content extension is declaratively
      * or programmatically made visible to the viewer.
      * @see INavigatorContentService#bindExtensions(String[], boolean) For more
      * information on what <i>visible</i> means.
      */
     public boolean isVisible(INavigatorContentDescriptor aContentDescriptor) {
         return programmaticVisibilityBindings.contains(aContentDescriptor
                 .getId())
                 || viewerDescriptor
                         .isVisibleContentExtension(aContentDescriptor.getId());
     }

     /**
      *
      * @param aContentExtensionId
      * The unique id of the content extension
      * @return True if and only if the given content extension is declaratively
      * or programmatically made visible to the viewer.
      * @see INavigatorContentService#bindExtensions(String[], boolean) For more
      * information on what <i>visible</i> means.
      */
     public boolean isVisible(String aContentExtensionId) {
         return programmaticVisibilityBindings.contains(aContentExtensionId)
                 || viewerDescriptor
                         .isVisibleContentExtension(aContentExtensionId);
     }

     /**
      * Return whether the given content extension is a root extension.
      *
      * @param aContentExtensionId
      * the id of the content extension.
      * @return whether the given content extension is a root extension
      */
     public boolean isRootExtension(String aContentExtensionId) {
         return programmaticRootBindings.contains(aContentExtensionId)
                 || viewerDescriptor.isRootExtension(aContentExtensionId);
     }

     /*
      * (non-Javadoc)
      *
      * @see org.eclipse.ui.navigator.IExtensionActivationListener#onExtensionActivation(java.lang.String,
      * java.lang.String[], boolean)
      */
     public void onExtensionActivation(String aViewerId,
             String [] theNavigatorExtensionIds, boolean isActive) {
         if (aViewerId.equals(viewerDescriptor.getViewerId())) {
             notifyClients();
         }

     }

 }

